docs: four "(a later slice)" comments describe features that shipped; delete them

Four source comments still promise a "later slice" for something that exists today. Each one is a sentence a reader trusts less the moment they notice the feature is already there (#253 cleaned up the first batch of these; these are the ones it missed). | Where | Says | Reality | |---|---|---| | `src/doberman/cli/main.py:958` (docstring of `doberman hook codex-pre`) | "Wire it in with ``doberman install-hooks --host codex`` (a later slice)." | `install-hooks --host codex` shipped; it's `_install_codex` in the same file. | | `src/doberman/hosthooks/claude_code.py:5` | "Wired in (see ``doberman install-hooks``, a later slice)" | `install-hooks` shipped long ago. | | `src/doberman/hosthooks/claude_code.py:59` | "scanned by the PostToolUse hook (a later slice)" | `doberman hook post` exists (`main.py`, the `post` command). | | `src/doberman/hosthooks/codex.py:52` | "``doberman doctor`` (a later slice) reports an installed Codex outside this range" | `doctor` has `_check_codex_version` (`src/doberman/cli/doctor.py:82`). | **What to do** 1. Delete the "(a later slice)" clause from each of the four comments so the sentence states what the code does now. Keep the rest of each sentence; only the promise goes. 2. `rg "later slice" src/` should then return nothing. If it finds a fifth, take that too. 3. Run `ruff format --check .` (a trimmed docstring can change line wrapping) and `pytest tests/unit/test_cli_help.py`; no test should need changing. Comments and docstrings only, no behaviour change. The `codex-pre` docstring is also the `--help` text, so that one is user-visible.